Apparatus for liquid treatment of flat materials

ABSTRACT

Plating or etching or other immersion treatment of lower portions only of horizontally fed, vertical positioned thin strips and arrays of workpieces is accomplished by recirculating electrolyte or the like through a bathtub provided with vertical slots to receive and discharge such workpieces. The rate of recirculation is such that an effective plating height well above the bottom of the vertical bathtub slots is maintained. A plurality of horizontally moving clamps support the workpieces and are electrically connected thereto as the workpieces move into, through, and out of the bathtub. These clamps are also electrically slidably connected to bus bars to form part of a complete electroplating circuit.

United States Patent Sabatka et al.

[4 1 Feb. 22, 1972 [54] APPARATUS FOR LIQUID TREATMENT OF FLAT MATERIALS[72] Inventors: Winston E. Sabatka, Lakeville; Wilhum M. Bloomquist,Minneapolis; Raymond W. Reinke, Rosemount, all of Minn.

[73] Assignee: Finishing Equipment and Supply Co., Inc.,

Bloomington, Minn.

[22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,467

[52] US. Cl ..134/l17,134/125,134/128, 134/ 130 [51] Int. Cl ..B05c3/10, B050 11/ 14, B08b 3/04 [58] Field oiSearch..134/48,75,117,118,125, 134/126, 128, 130

[56] References Cited UNITED STATES PATENTS 2,618,284 ll/l952 Purnell..l34/130 X Primary Examiner-Robert L. Bleutge Attorney-Burd, Braddock81. Bartz [57] ABSTRACT Plating or etching or other immersion treatmentof lower portions only of horizontally fed, vertical positioned thinstrips and arrays of workpieces is accomplished by recirculatingelectrolyte or the like through a bathtub provided with vertical slotsto receive and discharge such workpieces. The rate of recirculation issuch that an effective plating height well above the bottom of thevertical bathtub slots is maintained. A plurality of horizontally movingclamps support the workpieces and are electrically connected thereto asthe workpieces move into, through, and out of the bathtub. These clampsare also electrically slidably connected to bus bars to form part of acomplete electroplating circuit.

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PAIENIEDFEB22 mea; 643 670 SHEET 3 BF 5 INVENTORS WINSTON E. SABATKAWILBURN M. BLOOMQUIST Y RAYMOND w REINKE WfM APPARATUS FOR LIQUIDTREATMENT OF FLAT MATERIALS BACKGROUND OF THE INVENTION Electrolytictreatment of metals for the purpose of depositing a dissimilar metal ona substrate metal, for example, and treatment of metals chemically as toeat away undesired portions in the production of printed circuits" orother metallic articles has long been accomplished by batch methods.Such methods are always subject to certain inherent problems, and amajor one is the lack of adaptability to high volume, completely uniformwork production.

On some work pieces it is necessary that precious metals be deposited oncertain portions thereof while it is unnecessary and highly undesirablethat the entire piece be so treated. Batch methods or continuous processtotal immersion methods formerly utilized involved plating of theprecious metal on the entire piece in order to get the desired metal onthe desired surface. In instances where the surface area not needed tobe coated with the precious metal is substantial, the cost of preciousmetal wasted is excessive. Also, where it is desired to have a firstmetal plated up to a certain height on a workpiece of a second metal,and a third metal plated over the second to a lesser height, such pieceshave been impossible or impractical to produce by the aforementionedimmersion methods.

In the past, to plate or etch or otherwise treat a flat continuous stripof work material, the flat strip has been supported in a horizontalplane, run over a roller to carry it from the horizontal, verticallydown onto a roller situated inside of a bath, along through the bath,around through a further roller and vertically up out of the bath andonto the next work station. Certain difficulties in getting uniformplating or other liquid action simultaneously on both the bottom and topsurfaces are often encountered by this method. While the method can beused on strip materials which are fairly rugged and susceptible tobending without damage, such a method is difficult or impossible onextremely thin or otherwise fragile pieces which cannot stand bendingaction during the treating process.

SUMMARY OF THE INVENTION An apparatus made according to the inventioncan include at least one process cell consisting of a bathtub,collection tanks, and headers. A sump tank is fed from the collectiontank and a sump pump recirculates the electrolyte to the headers andback to the bathtub. The bathtub is provided with a pair of verticalaligned slots or openings at opposite ends thereof to permit workmaterial to be fed into one slot and out of the other. Diverging,vertical guide walls extending through and beyond each vertical slotprovide guidance to the work product and constriction to and laminaroutflow from the bathtub.

The rate of recirculation, the dimensions and shape of the space betweenthe guide walls, the volumetric displacement of the material beingtreated and the physical characteristics of the liquid all helpdetermine the equilibrium point for the liquid surface in the bathtub.This equilibrium point is adjusted precisely with respect to the workmaterial by means of adjusting screws which control the verticalpositioning of the bathtub.

In order to obtain uniform, and as much as possible turbulent, flow ofthe recirculating liquid back into the bathtub, the

sump pump connects to headers on both sides of the bathtub which openthrough a myriad of evenly spaced relatively small holes through acommon wall between each header and the bathtub.

The foregoing elements of the invention are important whether the liquidin the bathtub is for the purpose of cleaning, etching, rinsing,developing, painting, plating, deplating or otherwise treating thehorizontally moving, vertically positioned relatively narrow workmaterials.

Where electrolytic action is involved, an electrical plate or anodecovers over this area of liquid recirculation from the header, and theplate is provided with holes aligned with the header holes so as not toconstrict the flow of recirculating electrolyte. This anode can beconstituted as a metal screen.

A plurality of clamps are supported on a horizontal conveyor which ispositioned to move the clamps directly over the egress and exit slots ofthe bathtub. In the form of the invention shown, two parallel horizontalroller chains are utilized and their horizontal path is fixed by anglesor flanges on which they ride during the critical portions of theirpaths while they are supporting the clamps over the bathtubs. The clampsare supported with respect to the chains by horizontal wood slatsaffixed to the bottom of the two conveyor chains, and an electricalconnection extends from the electrically active jaw of each clamp to apoint along its wooden slat to where it is electrically connected to aspring-loaded, normally upwardly extending contactor or brush.

On the main frame of the machine, bus bars are situated in alignmentwith these contactors and have upwardly tapering end portions whichforce the spring-loaded contactors into firm electrical contact with thebus bars as they move therealong. These bus bars are positioned to makeelectrical contact with the clamp before the work connected to the clampenters the bathtub, to maintain this contact throughout its trip throughthe tub, and to relinquish the contact only after the work has left thetub. In this manner, a maximum dispersion of electrical current isobtained throughout continuous strip of work material, and the currentdensity throughout any one clamp is minimized.

These clamps include a fixed jaw fixedly mounted to the wood slat, and apivoted movable jaw resiliently urged toward the fixed jaw. Lowerportions of the jaws which might otherwise which might otherwise besubjected to deleterious action by the bath materials due to a splashingor even immersion are covered with an impervious coating of plastic orthe like, but one or both of the clamping ends of the jaws of the clampsare bare to allow electrical contact between the work material and thepump. Each movable jaw has an upwardly extending handle. A cam affixedto the main frame of the apparatus has a camming surface situated tocome to bear on each handle as the clamp moves along its path, to forcethe handle in direction to open the clamp where the work material isinserted, and then to allow the clamp to close on the work material. Asimilar camming device at the output end of the machine releases theclamp at the point where the work material is to come off the machine.

IN THE DRAWINGS FIG. 1 is a top plan view of one form of apparatus forpracticing the present invention;

FIG. 2 is a side elevational view of the apparatus of FIG. 1;

FIG. 3 is an enlarged fragmentary view of a portion of the left end ofthe machine as seen in FIGS. 1 and 2;

FIG. 4 is an enlarged fragmentary end elevational view of the machine asseen from the left of FIGS. 1, 2 and 3 with parts in sections and partsbroken away;

FIG. 5 is a fragmentary perspective view of portions of the left end ofthe apparatus as seen in FIGS. 1, 2 and 3 and showing the relationshipof one of the conveyor chains, the wood slats, the clamps, the clampopening and closing cam, and a continuous strip of work materialsupported in said clamps;

FIG. 6 is an enlarged fragmentary perspective view of one process cellshowing its relationship to the clamp, the work material passingtherethrough, the bus bar, and the electrical connections between theclamp and the sliding contactors and the bus bar;

FIG. 7 is the top plan view of the process cell of FIG. 6;

FIG. ,8 is a vertical sectional view taken on the line 8-8 of FIG. 7;

FIG. 9 is a vertical sectional view taken on the line 9-9 in FIG. 8; and

FIG. 10 is a transverse enlarged vertical sectional view of a clamp andthe end of the wood slat to which it is attached taken on the line 1010in FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS An apparatus for electrolyticplating of a continuous horizontally moving, vertically positioned stripof material is illustrated generally at 10. It consists of a main frame11 supported on a floor by legs 12. A plurality of process cells 13 aresupported for precise vertical adjustment with respect to the mainframe. In FIG. 1, two such cells are shown, one on one side of themachine and one on the other. In general, the action of each processcell as far as maintaining the level of liquid bath is concerned is thesame. However, in a particular process, each cell along the apparatuscan perform a different function. For example, a first cell canelectroclean the work, a spray rinse station of any usual or preferredconstruction can then clean both sides of the continuous work strippassing through, a second cell can consist of an acid bath to furtherprepare the work, and the third cell can then be for the electrolyticdeposit of gold, for example, on the workpiece. This can be followed bya reclaiming spray, two rinses, an alcohol spray wash, and a filteredair blowoff to dry the work.

Since all of the process cells act the same way as far as maintainingliquid level is concerned, a typical cell, namely one for use inelectrolytic depositing of metal, is here shown and described. In orderto present a typical machine, two separate apparatus mounted on the samemain frame are shown. A first processing line moves a verticallypositioned, continuous strip of horizontal material along a verticalplane generally shown by the arrow 14 (FIG. 1 while a second process isbeing performed on other work material along the plane of the arrow 15.In FIG. 1, the two process cells 13 along the two processing lines areshown to be in line with each other transversely of the apparatus, butit is to be understood that there is no necessity that this spacing bemaintained or that the same process be performed down each of the twolines. It is necessary only that the rate of flow of the work materialbe uniform inasmuch as the clamps carrying the work move with twoseparate conveyor chains, which chains are driven on common shafts tohave the same speed, as will be explained more fully.

Throughout the remainder of this description, the first process alongthe line of the arrow 14 will be described.

The process cell 13 includes a bathtub 17, two collection tanks 18 and19, and a pair of headers 20, extending longitudinally along upperportions of the bathtub 17. This tub is provided with an entrance endwall 33 having an entrance slot 21 and an egress end wall 35 havingegress slot 22 opening into the collection tanks 18 and 19 respectively.In turn, the end wall of the collection tank 18 is provided with anentrance slot 23 while the end wall of the collection tank 19 isprovided with an egress slot 24.

The collection tanks 18 and 19 are provided with drain pipes 25 and 26respectively, both of which open into a sump tank 27. As shown in sideelevational view in FIG. 2, and as shown schematically in FIG. 9, a sumppump 29 pumps the liquid from the sump tank through a supply pipe 30into the bottom of each of the headers. A throttle valve 31 may beprovided in the sump supply line at an appropriate location toaccurately control the flow into the headers to obtain a degree ofcontrol over the height of liquid in the bathtub.

As perhaps best seen in FIGS. 3, 6, 8 and 9, angle iron runners 40,forming part of the main frame 11, threadably support four manuallyoperable adjusting screws 41, having hand wheels 43. These screws, inturn, support transverse angle iron bolsters 42, which in turn supportthe cell 13 under the bathtub portion 17 thereof.

With sufficient flow through the sump pump 29 and supply pipe 30, thelevel of liquid in the bathtub will rise until an equilibrium isreached. Hand wheels 43 can be rotated to evenly raise or lower the cell13 and consequently raise and lower this equilibrium height of liquidwith respect to the main frame. This allows precise control of the depthof immersion of the work pieces in this liquid.

The flow from the headers into the bathtub is through a plurality ofrelatively small openings or holes 32 in the common walls 39 betweenthese headers and the bathtub.

It is to be understood that with these elements of the system, somedegree of operation of the invention would take place. The horizontalprogress of vertically supported workpieces through slots 21 and 22would result in the liquid acting on that portion of the work which wasbelow the bath liquid level.

Under certain conditions, there would still be some difficulties to thismode of operation, however. For this reason, the entrance end wall 32which is provided with the slot 21 has upper portions adjacent the slotcut away to provide a triangular weir 34. Similarly, egress end wall 35,which is provided with egress slot 22 is likewise provided with a weir36. It will be understood that these weirs, having throats substantiallyexactly on the same horizontal plane with each other, will tend to limitthe upper level of liquid in the bathtub 17 to this horizontal plane.

Even this refinement is not sufficient in some cases, however. With justthe slots 21 and 22, the weirs 34 and 36, the liquid flow through theslots would be a free fall flow, and a great amount of splashing intothe collection tanks would ensue. This would necessitate making thesecollection tanks substantially longer to insure that no liquid splashedout through the egress and entrance slots 23 and 24, respectively, ofthose tanks. This is undesirable, and in some cases, completelyunsatisfactory, as when it is necessary to wash off the work materialwithin a very short period of time after it leaves the bath. Elongationof the collection tank 19, for example, will result, at the speedsnecessarily used, in the work materials drying before they reach thespray station beyond the collec tion tank 19. Thus it is essential thatthe collection tanks be kept as short as possible.

In order to do this, a pair of vertical, diverging, funnellike guidewalls 37,37 are provided in the entrance slot 21, and a similar pair offunnellike vertical guide walls, 38,38 are positioned in the slot 22. Asbest seen in FIG. 9, these guide walls can be fastened into the endwalls 33 and 35 through the instrumentality of screws or stove bolts 95.By providing slotted openings 94 in the walls 33 and 35 a very preciseadjustment of the space between these guides can be obtained.

As illustrated in FIG. 8, and as will be understood from a considerationof FIGS. 6 and 7, the flow of liquid from the bathtub 17, through thespace between the guides 37,37 and 38,38 and specifically through thethroat portion'thereof and beyond has been found to be laminar incharacter. The drag of the diverging guide walls has been found to causethe upper surface of the water to bend as indicated in FIG. 8. Thisfriction, and the laminar flow, cause much of the energy of the liquidto be dissipated at the time the bottom or outer edge of the guide wallshas been reached, and no great difficulty with splashing or turbulencehas been encountered even with the relatively short collection tanks 18and 19.

These guide walls 37 and 38 also position the work material properly asit passes into the bathtub and out of it. This is particularly importantwhen a plurality of separate workpieces are being carried on edge, aswill be explained below.

Work materials are carried through the process cells and along theprocessing line of the apparatus by clamps 44. Each clamp is fixedlymounted as at 45 to a wooden slat 46 which in IIHITA Il'llh turn ismounted as at 47,47 to a pair of roller drive chains 48,48. The drivechains run over idler sprockets 49 which run on an axle 50 supported inbearing 51 on the main frame 11. This is best seen in FIG. 3. The otherends of the roller drive chains 48,48 run on drive sprockets on axle 52,which is driven by back geared motor 53 and the pinion, chain andsprocket drive 54. This is best seen in FIG. 2.

The clamp 44 includes a bifurcated fixed jaw 57 which is mounted to theslat 46 at 45, and a bifurcated pivoted jaw 58 pivotally mounted to thefixed jaw as at 59. A spring 60 urges the jaws towards closedrelationship to each other.

Mounted to the main frame 11, as seen in FIGS. 1, 2, 3 and 4 and asperhaps best seen in FIG. 5, is a clamp opening cam 62. The pivoted jaw58 of each clamp has an upstanding arm 61 integral with it. As eachclamp comes around the entrance end of the roller chain drive path, itsarm 61 is picked up by the camming surface of the cam 62 and, as itslides along this surface, the handle is forced in direction toward thewood slat which supports the clamp, and the jaws open up as best seen inFIG. 5. While the jaws are open, the work material being processed willbe drawn into position between the jaws by the action of other clampsworking along the horizontal conveyor path. When this relationship ofclamp to work material is established, the arm 61 reaches a part 63 thecam 62 which is bent to allow this arm 61 and the entire jaw 58, actingunder the urging of the spring 60, to move into clamping relationship tothe work.

As shown in FIG. 10, lower end portions of the clamp can be coated withimpervious plastic coatings 64 to prevent interaction of the metal jawsof the clamp with the electrolyte or other liquid being utilized in theprocess. At least some portion 65 of at least one of the jaws will beleft as bare metal, thus insuring a good electrical contact between theclamp and the work material held therein.

One means of automatically feeding a continuous strip of work materialfor processing is to provide a platform or turntable 68 on which issupported a coiled supply 69 of work material 70 to be processed. Inorder to start the feed of this material down the processing line, it isnecessary only that the first clamp beyond the cam 62 be manually openedand the work material 70 be properly positioned therein. Then the motordrive 53 is activated, and this first clamp will carry the work materialalong as subsequent clamps are applied to it.

1 At the output end of the apparatus, similar cams are provided torelease the work material, and it will be necessary to provide a powerdrive 72 for a takeup turntable 73 to collect the processed workmaterial.

To obtain electrolytic action, a first terminal from a source ofelectrical power 74, illustrated diagrammatically in FIG. 6 iselectrically connected by wires 76 to anodes 75 which are positioned inthe bathtub adjacent to each of the common walls 39,39 between theheaders and the bathtub 17.

A second terminal from this source of electrical power 74 is connectedby wire 71 to a bus bar 78,'also as diagrammatically shown in FIG. 6.This bus bar is supported on a wood block 79 which is affixed to themain frame 11 by brackets 80,80.

A wire 81 extends from the movable jaw 58 of each clamp 44 to haveelectrical connection with an associated contactor or brush 82 slidablymounted in its wooden slat 46. Each brush is urged in upward directionby a spring 83. As best seen in FIGS. 3 and 4, the bus bar 78 has anupturned camming end 84 in alignment with the contactors 82 in positionto force each of these contactors slightly downward against the spring83. at position before its clamp 44 carrying a particular portion of thework material is in position over the bathtub. This sliding electricalcontact between the contactor 82 and the bus bar 78 is maintained untilthe particular clamp has cleared vertical alignment with the bathtub.

ln-order to insure that the clamp will remain precisely in a horizontalplane as it carries the work materials through the tub, an angle bracket85 is provided on the main frame in position to support the bottomsurface of the roller chain 48.

As shown, the anode is constituted as a metal plate having openings 87therein in alignment with the openings 32 in the wall 39 between theheader and the bathtub.

Another structure of anode which is effective is formed of a screen orhaving the dimensions of a hardware cloth, thus providing the necessarymetal in parallel uniform proximity to both surfaces of the work as itpasses through the bathtub and still allowing for passage of theelectrolyte therethrough. Spaced parallel bars electrically connected toeach other will have somewhat the same effect.

In an electrolyte bath of IO feet in length, for example, the structureof the present invention has the advantage that clamps can be spaced sothat a large number of points of electrical contact are present betweenthe clamps and the work materials. Thus the concentration of current atany one point is kept to an absolute minimum. Such an arrangementprovides for very much less than the current density which must bepresent when there is but one contact with the work material at a pointoutside of the bathtub on the entrance side thereof and another point ofcontact outside of the bathtub on the egress side. The constitution ofthe clamps as each having two prongs further maximizes the number ofcontacts and minimizes the current density at any particular point ofcontact.

While the specification thus far has dealt primarily with continuousflat strips of material to be plated, the method and apparatus of theinvention may be used with equal effectiveness on flat individualsections of work materials. This is illustrated in FIG. 3 where one ofthe clamps 44 is also identified as clamp 88. This clamp is holding anindividual workpiece 89. This work piece includes a common metallicstrip 90 out from which fingers 91 extend. These fingers can be of thesame substrate metal as the piece 90, and can be formed in a stampingoperation, for example. In some instances, such a workpiece will beultimately used in the form as it is processed, and in other instancesbefore its ultimate use, the common metallic strip will be broken or cutaway to leave individual parts which are plated at certain desiredlocations. As an example, the workpiece 89 is shown as having beenplated twice. In this instance, the process cell shown in the drawing ofFIG. 3, instead of being for plating, could be for giving the alreadyplated piece a final cleaning path.

Assuming that the substrate metal is coated with copper up to the point92 and with gold up to the point 93, the workpiece 89 has been sentthrough a copper plating process cell in which the upper surface of theelectrolyte was in horizontal alignment with the point 92. This can beaccomplished by placing the work material higher up inside of the clamp88 or by changing the level of the process cell with respect to the mainframe through the instrumentality of adjusting screws 41, or by varyingthe electrolyte flow or some other factor listed above. Usually thelevel will be changed by adjustment of the screws 41. After the copperplating was accomplished, and any other necessary or desired stepsperformed, the workpiece 89 was sent through a process cell in which theupper level of the electrolyte was in alignment with the point 93, and alayer of gold, for example, was plated in the piece. Thus the resultingparts will have a plating of copper to the desired height and will havea plating of gold to the desired height, and no extra gold or copperwill be wasted on the pieces.

Either the individual workpieces such as 89 can be manually positionedon a guide under the clamp opening cam 62 to be picked up by a clamp 44;or an automatic feed (not shown) can support these pieces to be sopicked up. Each workpiece will be released from the apparatus by theopening of the clamp at the output end of the apparatus.

Uniform plating, cleaning, etching or other action will be obtained inthe use of the method and apparatus of the present invention inasmuch asthere is a vigorous mixing action involved when the liquid falls fromthe collector tanks, into the sump tank, is pumped rapidly through thesump pump, and discharged through a header of substantial volume throughthe many tiny openings to have a washing, turbulent,

scrubbing action against the work material progressing slowly in frontof it. There is, in other words, no way in which isolated pockets ofspent and concentrated electrolyte can accumulate. Thus, the particularsolution batch of liquid can be used right up until the time it isalmost entirely spent.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for processing only predetermined lower portions ofrelatively flat workpieces through a liquid bath, said apparatus havinga main frame, a bathtub mounted on said main frame and having a pair ofend walls at opposite ends thereof, each of said walls being providedwith relatively narrow vertical slots of width sufficient to pass saidworkpieces when moved vertically and on edge, means supported on saidframe to support said flat workpieces to be in vertical aligned edgewiserelationship to the slots and to cause lower portions of said workpiecesto move through a first entrance slot, said tub and a second egressslot, a pair of collection tanks posi-.

tioned to receive liquid flowing out from said tub through said slots,means for recirculating said liquid from said tanks into said tub at arate sufficient to establish and to maintain a predetermined liquiddepth in said tub above the bottom of said vertical slots and to exactlyencompass the predetermined lower portions of said workpieces.

2. The combination as specified in claim 1 and means for preciselyadjusting the vertical positioning of said bathtub with respect to saidmeans to support and move said workpieces.

3. The combination as specified in claim 1 wherein said means torecirculate includes at least one header on a side of said tub to beinfacing, spaced, parallel relation to the path of work material movingtherethrough, a common wall separating the interior of said tub from theinterior of said header, said common wall being provided with aplurality of holes to permit recirculating liquid to pass from saidheader into said tub.

4. The combination as specified in claim 3 and two sets of verticalguide walls, each set being positioned within one of said slots, andeach set extending divergingly outwardly from said tub in position toserve in said entrance slot as a guide to lead oncoming workpieces intosaid slot and to serve in said egress slot to tend to support emergingworkpieces as they move out of said tub.

5. The combination as specified in claim 4 wherein the angle ofdivergence is such as to limit liquid flow therethrough to laminar flow.

6. The combination as specified in claim 4 and means for accuratelyadjusting and fastening each pair of guide walls with respect to eachother to precisely control the maximum effective dimension of the slot.

7. The combination as specified in claim 1 wherein said means torecirculate includes a pair of headers, each situated on a side of saidtub to be in facing, parallel relation to the other on opposite sides ofthe path of the work material moving through the tub, common wallsseparating the interior of said tub from the interiors of each of saidheaders, said common walls being provided with a plurality of holes topermit recirculating liquid to pass from said header into said tub, saidrecirculating means also including a sump tank, drain conduits open froma bottom portion of the collection tanks into the sump tank, and a pumpand conduit means for pumping said liquid from said sump tank into theheaders.

8. The combination as specified in claim 7 and means for accuratelycontrolling the volume of liquid delivered by said pump thus toaccurately control the depth of liquid in said tub.

9. The combination as specified in claim 8 and means for preciselyadjusting the vertical positioning of said bathtubwith respect to saidmeans to support and move said workpieces.

10. The combination as specified in claim 1 wherein said means tosupport and move said flatwork pieces includes a horizontal conveyormounted on said main frame and adapted to move in a plane parallel to avertical plane passing through said bathtub slots and a workpiece clampmounted to move with said conve or.

ll. The com ination as specified in claim 10 wherein said clamp includesa fixed jaw fixedly mounted to move with said conveyor, a pivoted jawpivoted to said fixed jaw and resiliently urged into closingrelationship with it, an arm integral with said pivoted jaw andextending upwardly therefrom, a first-cam on said main frame inalignment with said pivoted jaw arm and adapted, before said material isprocessed, to force said arm in direction to open said clamp to hold itopen while work material is inserted therein and to allow said clamp toclose, a second cam on said main frame to open said clamp to permit workmaterial to pass therefrom when said material has been processed by saidapparatus.

12. The combination as specified in claim 1 wherein an upper portion ofsaid slots of each of said entrance and egress walls is enlargedbeginning at a point marking the predetermined liquid depth in the tubto provide for the rapid increase in the cross-sectional size of saidslots.

min; A". m

73 3 UNITED STATES I PATENT TOFFI CE CERTIFICATE OF CORRECTION PatentNo. 3,643,670 Dated February 22, 19.72

lnventofls) WINSTON E. SABATKA et a1 It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below':

Column 2, line 45, "which might otherwise" is repetitious.

Column 2, line 50, "pump" should be -clamp-.

fiigned and sealed this 13th day of June 1972.

Qttest:

EDL-IARD M.FLETGHER, JRa ROBERT GOTTSGHALK attesting OfficerCommissioner of Patents

1. Apparatus for processing only predetermined lower portions ofrelatively flat workpieces through a liquid bath, said apparatus havinga main frame, a bathtub mounted on said main frame and having a pair ofend walls at opposite ends thereof, each of said walls being providedwith relatively narrow vertical slots of width sufficient to pass saidworkpieces when moved vertically and on edge, means supported on saidframe to support said flat workpieces to be in vertical aligned edgewiserelationship to the slots and to cause lower portions of said workpiecesto move through a first entrance slot, said tub and a second egressslot, a pair of collection tanks positioned to receive liquid flowingout from said tub through said slots, means for recirculating saidliquid from said tanks into said tub at a rate sufficient to establishand to maintain a predetermined liquid depth in said tub above thebottom of said vertical slots and to exactly encompass the predeterminedlower portions of said workpieces.
 2. The combination as specified inclaim 1 and means for precisely adjusting the vertical positioning ofsaid bathtub with respect to said means to support and move saidworkpieces.
 3. The combination as specified in claim 1 wherein saidmeans to recirculate includes at least one header on a side of said tubto be in facing, spaced, parallel relation to the path of work materialmoving therethrough, a common wall separating the interior of said tubfrom the interior of said header, said common wall being provided with aplurality of holes to permit recirculating liquid to pass from saidheader into said tub.
 4. The combination as specified in claim 3 and twosets of vertical guide walls, each set being positioned within one ofsaid slots, and each set extending divergingly outwardly from said tubin position to serve in said entrance slot as a guide to lead oncomingworkpieces into said slot and to serve in said egress slot to tend tosupport emerging workpieces as they move out of said tub.
 5. Thecombination as specified in claim 4 wherein the angle of divergence issuch as to limit liquid flow therethrough to laminar flow.
 6. Thecombination as specified in claim 4 and means for accurately adjustingand fastening each pair of guide walls with respect to each other toprecisely control the maximum effective dimension of the slot.
 7. Thecombination as specified in claim 1 wherein said means to recirculateincludes a pair of headers, each situated on a side of said tub to be infacing, parallel relation to the other on opposite sides of the path ofthe work material moving through the tub, common walls separating theinterior of said tub from the interiors of each of said headers, saidcommon walls being provided with a plurality of holes to permitrecirculating liquid to pass from said header into said tub, saidrecirculating means also including a sump tank, drain conduits open froma bottom portion of the collection tanks into the sump tank, and a pumpand conduit means for pumping said liquid from said sump tank into theheaders.
 8. The combination as specified in claim 7 and means foraccurately controlling the volume of liquid delivered by said pump thusto accurately control the depth of liquid in said tub.
 9. Thecombination as specified in claim 8 and means for precisely adjustingthe vertical positioning of said bathtub with respect to said means tosupport and move said workpieces.
 10. The combination as specified inclaim 1 wherein said means to support and move said flatwork piecesincludes a horizontal conveyor mounted on said main frame and adapted tomove in a plane parallel to a vertical plane passing through saidbathtub slots, and a workpiece clamp mounted to move with said conveyor.11. The combination as specified in claim 10 wherein said clamp includesa fixed jaw fixedly mounted to move with said conveyor, a pivoted jawpivoted to said fixed jaw and resiliently urged into closingrelationship with it, an arm integral with said pivoted jaw andextending upwardly therefrom, a first cam on said main frame inalignment with said pivoted jaw arm and adapted, before said material isprocessed, to force said arm in direction to open said clamp to hold itopen while work material is inserted therein and to allow said clamp toclose, a second cam on said main frame to open said clamp to permit workmaterial to pass therefrom when said material has been processed by saidapparatus.
 12. The combination as specified in claim 1 wherein an upperportion of said slots of each of said entrance and egress walls isenlarged beginning at a point marking the predetermined liquid depth inthe tub to provide for the rapid increase in the cross-sectional size ofsaid slots.